Communication systems typically include a plurality of communication units, such as mobile or portable radio units and dispatch consoles that are geographically distributed among various repeater sites and console sites. The communication units wirelessly communicate with the repeater sites and each other, and are often logically divided into various subgroups or talkgroups. Communication systems may be organized as trunked systems, where a plurality of communication resources is allocated amongst multiple users or groups by assigning the repeaters within a radio frequency (RF) coverage area on a call-by-call basis, or as conventional (non-trunked) radio systems where communication resources are dedicated to one or more users or groups. In trunked systems, or in mixed trunked and conventional systems, there is usually provided a central controller (sometimes called a “zone controller”) for allocating communication resources among multiple sites. The central controller may reside within a single device or multiple devices and may be located at a fixed equipment site or may be distributed among the repeater or console sites.
Traditionally, the repeater and console sites were linked via a circuit-switched architecture, through dedicated or on-demand circuits to a central radio system switching point (“central switch”). More recently, communication systems are using packet-switched networks where information that is to be communicated between endpoints is divided into packets and transported by various routers forming an Internet Protocol (IP) network. For example, communication systems using packet-switched networks are described and claimed in U.S. Pat. No. 6,141,347, titled “Wireless Communication System incorporating Multicast Addressing and Method for Use” and U.S. Pat. No. 6,647,020, titled “Methods for Implementing Talkgroup Call in a Multicast IP Network,” each of which is assigned to the assignee of the present invention and incorporated herein by reference in its entirety.
Packet-switched networks are sometimes called “connectionless” networks because they do not provide dedicated bandwidth or circuits between endpoints, but rather permit communications between multiple endpoints to proceed concurrently over shared paths or connections. For practical reasons, certain of the shared links may be sized to accommodate fewer endpoints than may desire to participate in a call. As an example, console sites in Motorola's SMARTZONE™ communication systems may include up to 30 operator positions having “select” and “unselect” speakers for monitoring up to 64 talkgroups, either passively (i.e., low volume in the “unselect” speaker) or actively (i.e., with “select” audio or high volume “unselect” audio). However, the console site links are typically configured with no greater than a T-1 or E-1 link. If all the talkgroups become active, the bandwidth required to monitor all of the talkgroups far exceeds the available bandwidth and typically, the excess calls will be “busied,” or denied use of the link until bandwidth becomes available. Moreover, it is possible that the available bandwidth is consumed by relatively low priority calls (e.g., passively monitored talkgroups), causing relatively high priority calls (e.g., actively monitored “critical” talkgroups) to be busied.
Accordingly, to the extent shared links of a packet-based communication system have limited available bandwidth, it would be desirable for a method of call control that allocates priority level(s) to requested calls, such that the limited bandwidth of the shared link(s) is allocated to higher priority calls before lower priority calls. Particularly in a packet based communication system having console site link(s) with limited available bandwidth, it would be desirable to dynamically associate a high priority level to certain console calls (e.g., critical talkgroups), such that the limited bandwidth of the console site link(s) is allocated on a priority basis for the high priority calls. The present invention is directed to satisfying these needs.